1. Field of the Invention
The present invention relates to novel cosmetic and/or therapeutic compositions for topical application to mammalian subjects, comprising at least one .alpha.-pyrone as the active principle thereof, and to the use of such novel compositions for inducing and stimulating hair growth and/or retarding hair loss.
2. Description of the Prior Art
In human subjects hair growth and renewal are principally determined by the activity of the hair follicles. This activity is cyclic and essentially entails three phases, namely, the anagen phase, the catagen phase and the telogen phase.
The active anagen phase, or growth phase, which lasts for several years during which the hair elongates, is succeeded by a very short and transient catagen phase and then a rest or quiescent phase, designated the telogen phase, which lasts for a few months.
At the end of the rest period, the hairs are shed and another cycle begins anew. The head of hair is hence being constantly renewed and, of the approximately 150,000 hairs on a human head, approximately 10% are at rest at any given instant and thus will be replaced in a few months.
In a large number of cases, early hair loss occurs in genetically predisposed subjects, and it affects men in particular. This applies, more especially, to androgenetic or androgenic or, alternatively, androgeno-genetic alopecia.
This alopecia is essentially due to a disturbance of hair renewal, which initially gives rise to an acceleration of the frequency of the cycles at the expense of the quality of the hairs, and then of their quantity. There is a gradual depletion of the head of hair through regression of so-called "terminal" hairs at the down stage. Some regions are affected preferentially, in particular the temporal or frontal areas in men, and a diffuse alopecia of the crown is observed in women.
Compositions that eliminate or reduce the effects of androgenetic alopecia and, in particular, that induce or stimulate hair growth or decrease hair loss have long been considered desiderata in the cosmetic and pharmaceutical industries.
In this regard, a large number of very diverse active compounds have been suggested for such purposes, for example, 6-amino-1,2-dihydro-1-hydroxy-2-imino-4-piperidinopyrimidine and derivatives thereof, as described, more especially, in U.S. Pat. No. 4,139,619. Nonetheless, considerable research and development is continuing in this art in quest of yet other such valuable active agents.